The conventional domestic, gas-fired water heater includes a generally cylindrical tank to contain water to be heated and a gas burner is located beneath the lower head of the tank. Waste gases of combustion generated by combustion of the gas, are discharged through one or more flues which extend upwardly through the tank. Heat is transferred from the combustion to the water in the tank as the heated gases pass across the bottom head and the flues.
To decrease the overall height of the water heater, it has been proposed to make the burner relatively shallow in vertical dimension, and to utilize a burner head of substantial diameter in which the gas is discharged through a plurality of ports arranged in a circular pattern so that the flame will be projected outward, horizontally beneath the lower head of the tank.
The lower head of the conventional gas fired water heater is upwardly concave so that the waste gases of combustion generated by the burner, which is located beneath the lower head, will be funneled radially inward to the central flue or flues. The use of a concave lower head has certain disadvantages in that it reduces the volume per unit length of the tank, as compared to a convex lower head, and requires the use of heavier gauge metal than a convex lower head. In addition, the concave lower head is not usually insulated because of the high temperature of the waste gases of combustion that it funnels into the flue or flues.